There are various known methods for producing fine particles and particularly for producing nanosize inorganic powders. Such particles and powders are used in diverse product applications such as thickeners for house paint, the manufacture of sintered parts such as valve seats for automobile engines, etc.
The prevalent processes for producing such small particles include flame-spraying, spark discharge, chemical precipitation, atomization and gas disassociation-collision-coalescence techniques. These known methods are disadvantaged in that they provide only limited control over the size, shape, structure and chemical composition of the resulting particles and powders. Therefore, for the most part, the prior powders have been relegated to the mundane uses described above; they have not been used to any great extent in more sophisticated applications such as in resonant optical filters, inorganic color pigments, ultra whiteners, catalytic agents, etc., where precise control over the size, structure and composition of the particles is of paramount importance.
Prior powder production techniques are disadvantaged also because they consume a relatively large amount of energy. Therefore, they are not suitable for high volume powder production where low cost is an important consideration.